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Measuring interference and noise power using non-content burst periodsRelated Patent Categories: Pulse Or Digital Communications, Systems Using Alternating Or Pulsating Current, Plural Channels For Transmission Of A Single Pulse TrainMeasuring interference and noise power using non-content burst periods description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070183522, Measuring interference and noise power using non-content burst periods. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims the benefit of the U.S. Provisional Application, Ser. No. 60/772,300, entitled "Noise and Interference Measurement" and filed on Feb. 9, 2006. TECHNICAL FIELD [0002] The embodiments provided herein relate generally to communication systems, and more specifically to measuring interference and noise in wireless receivers. BACKGROUND [0003] In wireless communication systems, the quality of the signal depends in large part on the amount of noise measured at the receiver antenna. In these systems, the noise figure is the ratio of the output noise power to the thermal noise in the input termination at standard noise temperature. The noise figure thus represents the ratio of actual output noise to that which would remain if the device itself was noise free, and provides an indication of the performance of a radio receiver. The noise power is typically used to denote the cumulative effects of noise figure at the receiver and the ambient (e.g. non-system) interference. The knowledge of noise power at the receiver is crucial for several blocks in the transceiver chain, which include, but are not limited to demodulation, decoding, power control, link adaptation, and similar operations. [0004] In general, there are three main sources of noise at the receiver antenna: (1) ambient (non-system) noise or interference, which is at or near the same operating frequency range of the desired signals; (2) circuit noise, which is noise introduced or picked up by the circuits or blocks in the RF (radio frequency) stage of the receiver itself; and (3) system or system-like interference, which is introduced by other transmitters or sources of desired signals for other receivers, but not for a particular receiver. In order to design and build effective wireless receivers, it is important to know or at least be able to accurately estimate or measure the signal-to-interference-plus noise ratio (SINR) in order to ensure communication quality or rate of transmission in a wireless link. The SINR level may differ depending on the location of a receiver within a cell, sector or other geographical characteristic of the wireless system, and can also vary depending upon the composition or amount of noise versus interference, or vice-versa. [0005] For wireless transmission systems that utilize OFDM (Orthogonal Frequency Domain Modulation) schemes or similar cellular systems, users who are on or near the boundaries between cells or sectors usually have low SINR ratios because of strong interference from terminals neighboring cells or the large distance from the basestation (transmitter). A multi-user version of OFDM is OFDMA (Orthogonal Frequency Division Multiple Access), which assigns subsets of subcarriers to individual users, thus allowing simultaneous low data rate transmission from several users. OFDMA systems may employ a "frequency reuse-one" technique, in which every cell and sector is free to utilize all of the subcarriers and symbols used in other cells and sectors. Such a system can have significant interference between sectors and cells, especially at the boundaries. In systems with lower frequency reuse, the interference may be reduced at the sector and cell boundaries, but can appear elsewhere. One issue with regard to OFDMA systems with reuse-one (or "reuse-1") mechanisms is the task of accurately measuring the noise and interference levels. In reuse-one systems, all of the subcarriers are filled with data and pilot traffic from the subscribers. In such a system, or other similar systems, it is difficult to isolate the noise and interference in specific subcarriers. One present method involves cancelling a receiver's signal to measure the remaining noise and interference. Such a cancellation process, however, is not optimum for certain systems or receivers, as some of the original signal may be injected into the measurements. It is desirable, therefore, to provide a system of measuring noise and interference that does not include or implicate the receiver's own signal. BRIEF DESCRIPTION OF THE DRAWINGS [0006] Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: [0007] FIG. 1 illustrates a wireless system that includes a noise and interference measurement system, under an embodiment. [0008] FIG. 2 illustrates the transmission of burst traffic in a network incorporating a noise and interference measurement method, according to embodiments. [0009] FIG. 3 illustrates an example of a time-frequency schedule for OFDM transmission using dummy bursts in a downlink subframe, according to an embodiment. [0010] FIG. 4 illustrates an example of a time-frequency schedule for OFDM transmission using dummy bursts in an uplink subframe, according to an embodiment. [0011] FIG. 5 is a block diagram of a receiver circuit that includes a noise power measurement system, under an embodiment. INCORPORATION BY REFERENCE [0012] Each publication, patent, and/or patent application mentioned in this specification is herein incorporated by reference in its entirety to the same extent as if each individual publication and/or patent application was specifically and individually indicated to be incorporated by reference. DETAILED DESCRIPTION [0013] Embodiments disclose a method of measuring noise and interference within transceivers of an OFDM wireless transmission system, or similar communication system, including a number of receivers communicating with one or more base stations in cell or sector arrangements. The transmitter schedules a transmission burst for a non-existent user (receiver) using wireless transmission traffic. In an OFDM system, this corresponds to a certain set of subcarriers in the time/frequency arrangement. Thus, in the receive frame structure, the data and pilot subcarriers are guaranteed to be only noise and interference from adjacent sectors. The receiver can accurately measure the noise and interference without needing to cancel out the transmitted signal. Therefore, the system is assured that there is no desired signal as part of this measurement. The noise and interference measurement process can be appropriately scheduled so that it does not impact the overall throughput of the system. This mechanism creates a deterministic place (in time and/or frequency) within the transmission, where no desired signal is required. [0014] FIG. 1 illustrates a wireless system that includes a noise and interference measurement system, under an embodiment. In system 100, a first base station or similar wireless transmitter 102 transmits radio or similar wireless signals 106 to a plurality of transceiver terminals 104, 106, and 108 that are within a cell or sector intended for reception of such desired signals 105. For purposes of discussion, the terminals 104-108 that are within the intended range of transmissions from the basestation 102 are referred to as "target terminals" or "assigned terminal," as distinct from unintended terminals, such as terminals 110 and 112. Thus, as shown in FIG. 1, the signal from basestation 102 may also be picked up by these other terminals 110 and 112, which are properly within the range of a second base station 114. Since terminals 110 and 112 are intended only to receive desired signals from basestation 114, the signals 109 received at these terminals constitute interference with the desired signals. If the terminals 110 and 112 are near the boundary of the sector dividing basestations 102 and 114, the interference signals 109 the SINR value due to the interference signals may be unacceptably high. Other sources of spurious signals that can affect the SINR of receivers 110 and 112 can be other types of interference or noise, such as noise signal 113. As used herein, the term "noise" means ambient noise, RF noise, and noise from other sources that may interfere with the desired signal, but that are distinct from actual signals from other transceivers in the system that are not desired, and which are referred to as "system-like" interference. Thus, each terminal in FIG. 1 can receive a signal that is a composite of the desired signal plus noise plus interference. That is S=D+I+N, where S is the received signal, D is the desired signal, I is the interference and N is the noise. Embodiments of the noise and interference measurement system measure the I+N components of the received signal, S by providing a mechanism of measurement that eliminates the effect of the desired signal, D. [0015] The terminals illustrated in system 100 of FIG. 1 may be subscriber stations or any transceiver (transmitter/receiver) device that is capable of communicating over bi-directional links to one or more of the basestations. Embodiments of the noise and interference measurement process work with both uplink (terminal-to-basestation) links, as well as downlink (basestation-to-terminal) transmissions. [0016] In OFDM and similar systems, the SINR values directly affect the quality or rate of communication. The amount of noise and system-like interference in the signal determines the quality of the transmission link and generally dictates how much data can be carried on the line. Such information can be used in various network management processes, such as link adaptation, power control, demodulation, decoding, and the like. Thus, in order to implement measures that can filter out or compensate for such interference and noise affects, it is important to be able to accurately measure the noise and interference levels in such systems. [0017] In one embodiment, system 100 of FIG. 1 utilizes data transmission based on frequency-division multiplexing (FDM), where each frequency sub-channel carries a separate stream of data. In a specific embodiment, OFDM (Orthogonal frequency-division multiplexing) is used. In OFDM, the sub-carrier frequencies are selected so that the modulated data streams are orthogonal to one another. This orthogonality allows for high spectral efficiency and simplifies transceiver design since separate filters are not needed for ach sub-channel. In general, OFDM is a modulation technique used in 802.11a WLAN, 802.16 and WiMAX technologies for transmitting large amounts of digital data over a radio wave. OFDM works by splitting the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. OFDM generally reduces the amount of crosstalk in signal transmissions. [0018] In a further embodiment, Orthogonal Frequency Duplex Multiple Access (OFDMA) systems are used. In an OFDMA system, time and frequency are divided into sub-units called symbols (in time f) and subcarriers (in frequency k). The basestation typically assigns multiple time symbols and subcarriers to carry the data from the basestation to the terminal. Each terminal within a sector is usually assigned a distinct subset of available symbols and subcarriers, which is denoted a "slot." The number of subcarriers and symbols, and the level of modulation, which is usually a function of the SINR, determines the data rate to or from the terminal. Continue reading about Measuring interference and noise power using non-content burst periods... 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